His learnings from 14 years at Google. Surely we've all learned things working for employers or with engineers that don't do a thing well.
In 14 years he probably also experienced great engineers come and go and start other successful businesses they very likely did not run exactly like Google.
Reporting on averages is fine but you've made the mistake of thinking that average is representative of anyone. In all likelihood salaries are not normally distributed around that average, and we'd instead find a low hump (rural) and a high hump (urban, suburban).
How is this true for generally appreciating assets like a house? It makes sense for commodities but until location and style don't matter I'm unconvinced there's a such thing as cost driving price in the housing market on any timeline.